Such electrical cables are used for the conveyance of large currents with high frequencies in aircraft and in the ground. By means of the overall symmetrical structure and the phase construction distributed over two conductors, they also have symmetrical and optimally reduced inductive voltage drops with a minimized skin effect, and so are used especially for longer stretches. In aircraft in particular, the supply of electricity with high-frequency current is well known to offer the advantage that as a result, lighter generators, engines and similar, in particular inductively acting components and equipment can be used in the aircraft.
With the previously known electrical cables of this type, the neutral and/or return conductor is made in the form of a one-part, solid or flexible neutral wire, the symmetrical structure of the cable meaning that the neutral wire is guided in the center of the cable. These known electrical cables totally satisfy the requirements if they are laid in a fixed manner.
When using the cable as a flexible service cable, as is the case when using the same as an electrical supply cable for aircraft, when not being used they are rolled up on reels or upon docking they are unrolled by the aircraft and are then pulled over the asphalt surface or similar. The case then arises where there is an active single conductor in the middle of the cable which is subjected to strong mechanical loading due to torsion because the supply cable is subjected recurrently to bending stress due to the repeated rolling up and unrolling.
This results in the risk of the neutral and/or return conductor of the cable being damaged by the strong bending stress, and so the cable becomes inoperable. In the past attempts have been made to compensate for this disadvantage by a mechanically reinforced core in the central neutral wire. However, this type of construction may nevertheless lead to breakage of the central conductor depending on the loading and life span of the cable, but at a later point in time than with comparable electrical cables with an unreinforced central conductor.
With generic cables the neutral conductor generally only has half the cross-section of the phase conductors (each with 2 phases). In particular, since single-phase asymmetrical consumers with connected power supplies on board bring about an addition to the harmonic waves that are generated in the neutral conductor, the skin effect, and so the loading, is disadvantageously increased in the latter.